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As part of the framework of the EFEDA (Echieval field experiment in a desertification threatened areal experiment, an 11-day data set including atmospheric Forcing, turbulent fluxes and soil water monitoring was gathered on a bare soil site, characterized by a large diurnal cycle of temperature, and with very dry conditions near the surface, A version of the SiSPAT (Simple Soil Plant Atmospheric Transfer) model, restricted to bare soil, was applied to this data set. The first objective was to validate model results against observations. This was restricted somewhat by the narrow range of soil moisture variations during the 11 days of the simulation. In addition some discrepancies were observed between total evaporation as calculated from neutron probe measurements and micrometeorological ones. However, because the SiSPAT results were more in agreement with evaporation calculated from soil water balance, it was assumed that the model could be used as a tool to investigate the mechanisms of the water movement and evaporation within the soil under such dry conditions. In the first 25 cm of soil, vapour flux is the most important transfer term, and the evaporation front (change of phase from liquid to vapour) can be localized at this depth. The contribution of temperature gradients to mass Bur is also found to be important, and tends to lower the total evaporation at the surface by creating a downward vapour flux component which partly cancels the upward one induced by large matric potential gradients at the soil surface. (C) 1997 Elsevier Science B.V.